A calibration projective for videomicrophotometry will be designed. It will allow control over the match between pixel resolution in the microscope, and the resolution of the videocamera. The design will also allow maintenance of exact magnification, even when high dry objectives with coverglass correction rings are used, and the design will allow elimination of spherical aberration due to preparation deficiencies, thus restoring high contrast and improved microphotometry. The design will be based on a zoom system with a built-in spherical aberration corrector. It will fit standard research microscopes, and accept videocameras via a standard C-mount. A pilot model will be fabricated, and tested in a clinical pathology laboratory.